Abstract
To succeed at a sport, athletes must manage the biomechanical trade-offs that constrain their performance. Here, we investigate a previously unknown trade-off in soccer: how the speed of a kick makes the outcome more predictable to an opponent. For this analysis, we focused on penalty kicks to build on previous models of factors that influence scoring. More than 700 participants completed an online survey, watching videos of penalty shots from the perspective of a goalkeeper. Participants (ranging in soccer playing experience from never played to professional) watched 60 penalty kicks, each of which was occluded at a particular moment (−0.4 s to 0.0 s) before the kicker contacted the ball. For each kick, participants had to predict shot direction toward the goal (left or right). As expected, predictions became more accurate as time of occlusion approached ball contact. However, the effect of occlusion was more pronounced when players kicked with the side of the foot than when they kicked with the top of the foot (instep). For side-foot kicks, the direction of shots was predicted more accurately for faster kicks, especially when a large portion of the kicker’s approach was presented. Given the trade-off between kicking speed and directional predictability, a penalty kicker might benefit from kicking below their maximal speed.
Highlights
Sport scientists commonly measure maximal performances such as fastest speed, highest leap, or farthest throw, because such parameters are thought to reflect performance in a game or event
Unpredictability is advantageous, and soccer players are more likely to score on a penalty kick if they can disguise the direction of the kick [7]
As the included participants did not differ in the proportion of correct responses based on soccer playing experience over the age of 18 (Figure 3), this variable was not included in the generalised linear model (GLM)
Summary
Sport scientists commonly measure maximal performances such as fastest speed, highest leap, or farthest throw, because such parameters are thought to reflect performance in a game or event. Throwing darts [4], kicking soccer balls [5], and pitching in baseball or cricket [6] are all subject to a trade-off between speed and accuracy. Sporting success does not rely on maximal performance but is affected by trade-offs that can be managed to optimise overall success. A potential trade-off between the speed and unpredictability of an action could influence success in penalty kicks. In this situation, unpredictability is advantageous, and soccer players are more likely to score on a penalty kick if they can disguise the direction of the kick [7]. Goalkeepers use cues presented by the kicker to predict shot direction before the ball moves [8,9,10]
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